8251

• UCREFRP Catalog Number: 8251
• Author: Rakowski, C. L. and J. C. Schmidt.
• Title: The Geomorphic Basis of Colorado Squawfish Nursery Habitat in the Green River Near Ouray, Utah.
• USFW Year: 1996.
• USFW - Doc Type: #93-1070,
• Copyright Material: NO

Draft Fmal Completion Report to UDWR for Contract #93-1070, Amendment 3

8

UI'ERATURE REVIEW

Sand-bedded rivers have been the focus of much study, often because of their impact on humans. While early

engineering studies focused on reducing the impacts of flooding and migrating rivers on human structures,

geomorphologists have endeavored to improve the understanding of why and how rivers form, migrate, and change, both

longitudinally and temporally. Only recently have geomorphologists combined their efforts with biologists and

ecologists to discern the effects of physical attributes and changes in those attributes on the ecology of river systems.

Geomorphology of Sand-bedded Rivers

Self.formed cbannels

Continually adjusting streams that flow within banks composed of material previously transported by the river

are termed self-formed channels and are the focus of long-standing geomorphic research. The Green River within the

alluvial Ouray NWR reach is an example of a self-formed channel. For self-formed channels, the channel form at a

given cross section is determined by discharge, quantity, and character of the sediment in transport, and the bank and

bed characteristics (Leopold and others, 1964). Consequently, in channels with a moveable bed and banks, channel

form results from the dynamic equilibrium of bank stability, flow, and sediment transport (Leopold and others, 1964).

This relationship is dynamic because in natural rivers, neither flow conditions nor bank and bed material are static in

space or time. When channels meander, the form of a cross section is mllintained although its position may change

(Leopold and others, 1964).

Classic geomorphic research on self-formed streams such as Watts Branch (Maryland), Brandywine Creek

(pennsylvania), and Baldwin Creek (Wyoming) measured characteristic parameters of streams such as the spacing of

pools and riftles, distribution of sediment sizes on the bed, bedload movement, channel shape through meanders,

velocity distribution within cross sections, and the relationship between flood recurrence and bankfull channel size

(Leopold and others, 1964). While these studies quantified many geomorphic relationships, they did not reveal the

physical processes underlying those relationships. More recent work, at both large (kilometers) and small (meters)

scales, has endeavored to study and model the physical processes expressed as channel form.